1. Field of the Invention
The present invention relates to rectifier circuits, more particularly full-wave rectifier circuits, which are integrable on the same piece of semiconductor substrate material as the circuitry which they power.
2. The Prior Art
One of the most common circuit functions is that of the rectifier or diode. A diode will pass current of one polarity and will block current of the reverse polarity. Most electronic circuitry requires current and voltage of a defined polarity for correct operation and yet, electrical power is almost uniformly distributed throughout the world in each country by means of AC grids operating with 50 to 60 Hz voltage sine waves.
Consequently, almost every piece of electronic equipment obtaining power from centrally-distributed power systems requires a means of converting AC power to DC power. This equipment includes data processing equipment, communications equipment and domestic appliances and a host of other devices. Usually this conversion from AC to DC power is achieved using multiple diodes in either a full-wave or half-wave configuration.
Rectifier circuits are well-known for converting AC to DC. A half-wave rectifier system only converts AC power to a DC output during the period that the AC signal is one polarity whereas the full-wave rectifier provides a DC output during either polarity swing of the AC input voltage. In many cases the full-wave system is preferable because of lower peak current since it conducts for twice the time on both positive and negative excursions of the AC input signal. It thus has reduced smoothing requirements since the AC ripple on the output is at twice the AC input frequency of the half-wave rectifier. This results in lower system costs.
The recent miniaturization revolution has been brought about by introduction of the integrated circuit, which incorporates a plurality of semiconductor devices on the same piece of semiconductor substrate material. Integrated circuit elements have found their way into use in many products; refrigerators, washing machines, microwave ovens and television sets are but a few of the many products which incorporate microprocessors to enhance their functionality. Many if not most of these products take power from the AC power supply to homes and businesses. At power levels in the neighborhood of 1 watt or less it becomes economically advantageous to integrate a rectifier or complete power supply onto the same semiconductor substrate as the circuitry it drives.
The provision of integrated components and subassemblies make these products easier and more economical to produce. The function of the full-wave rectifier, although simple in concept, has to date been extremely difficult to integrate using any of the common junction isolated semiconductor integrated circuit technologies because of interaction between the four diodes. To date, most full-wave rectifier bridges or other full-wave rectifier circuits contain four individual diodes connected to a four lead package. There thus exists the need for a diode equivalent full-wave rectifier circuit which can be integrated on the same semiconductor substrate as all or a portion of the circuitry which it drives.